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Super grade ammonium paratungstate is ammonium paratungstate with grade of APT-0, which is divided by national standard. Generally, traditional process to prepare high-purity ammonium paratungstate is first to dissolve super grade ammonium paratungstate by ammonia-dissolving method, and then evaporation recrystallization. The high-purity APT produced by traditional process has the disadvantages as follows: The energy consumption is high and the comprehensive recovery rate of resources is low. Also, equipment and investment are increased when compared with new processing technology, so that…

Grade 1 ammonium paratungstate is a national standard product of APT with grade of APT-1. The ammonium paratungstate may be obtained by the process of losing ammonia in ammonium tungstate solution. Its chemical equation is as follows: 12(NH4)2WO4→5(NH4)2O?12WO3?nH2O+(7-n)H2O+14NH3↑ Ammonium tungstate solution is not stable, so that water and ammonia escape when it is heated, and therefore ammonium paratungstate is continuously generated in solution. During this process, ammonium paratungstate changes from unsaturation to saturation to reach a stable state. Under the…

APT crystalline mother liquor’s main components are ammonium chloride, ammonium tungstate, a small amount of sulfur ions and sulfate ions. Tungsten and ammonia in mother liquor of APT crystal can be recovered by adopting one-step method, calcium hydroxide or calcium oxide as calcium source and caustic source. The one-step method has the advantages of simple process, easy availability of raw materials, and controllable cost. In a word, it provides a new way for resource utilization of APT crystalline mother liquor.…

Ammonium paratungstate hexahydrate’s chemical formula is (NH4)10H2W12O42?6H2O (APT?6H2O). Stability of Ammonium Paratungstate Hexahydrate It is key to generate ammonium paratungstate tetrahydrate ((NH4)10H2W12O42?4H2O or APT?4H2O) from aqueous solution of ammonium tungstate in the production of tungsten powders. Studies have shown that APT?6H2O can be formed under the generation of APT?4H20. Based on this data, it is assumed that APT?6H2O is metastable. Test to determine whether hexahydrate is metastable or not?! Under what conditions is it metastable? Find: The hexahydrate compound is…

Ammonium paratungstate tetrahydrate or APT?4H2O may be prepared by crystallization process from pure ammonium tungstate solution by batch process and continuous process. But APT?4H2O will lose part of crystal water in the drying process of this industrial production. Therefore, repeated crystallization is usually used to improve product quality. However, this method is limited by the slow dissolution of APT?4H2O. Ammonia Dissolves Ammonium Paratungstate Tetrahydrate At room temperature, APT?4H2O dissolves very slowly in aqueous ammonia. The dissolution temperature can be increased…

Large grain size ammonium paratungstate is an important intermediate product in the preparation of tungsten powder from tungsten concentrates. The physical properties of APT such as particle size, particle size distribution, and crystal morphology have an important influence on the physical and mechanical properties of its downstream products such as tungsten carbide, tungsten wire, and so on. Therefore, it is of great significance to study the influencing factors of grain size of APT. In the crystallization of APT, there are…

Ultrafine ammonium paratungstate may be prepared by microwave-ultrasonic cooperative evaporation crystallization method. Microwave-ultrasonic Cooperative Evaporation Crystallization to Prepare Ultrafine Ammonium Paratungstate 1. Experimental Equipment (1) XH-300A computer ultrasonic and microwave combined synthesis extraction instrument; (2) ZK-82B electric constant temperature drying oven; (3) UK Malvern laser particle size analyzer; (4) Miniflex X-ray diffractometer; (5) Netherlands Philips XL30 scanning electron microscope; (6) Diamond 6000 thermo-differential thermal analyzer. 2. Experimental Procedures A certain volume of ammonium tungstate solution with a concentration of WO3…

Coarse crystal ammonium paratungstate has found wider applications in many fields with the continuous development of new tungsten carbides and filament types. Therefore, it is of significance to study the preparation process of APT. Preparation of Coarse Crystal Ammonium Paratungstate At a water bath temperature of 60°C and under a certain degree of vacuum, a certain concentration of 300mL AT solution was poured into a 500mL 3-neck flask, stirred to evaporate to precipitate milky crystal nucleus, and heated within 1/2h…

High-calcium ammonium paratungstate means the ammonium paratungstate powder that has excessive Ca content. The phenomenon of excessive Ca content in APT products is likely to occur during the production of APT by ion exchange process. The high-calcium APT must be reprocessed as it will not only affect the quality of tungsten carbides, but also cause a waste of tungsten resources to some extent. The conventional process to treat ammonium paratungstate with severely Ca content has the disadvantages of long process…

Spherical-crystal ammonium paratungstate can be used to prepare high-performance tungsten heavy alloys, which has the characteristics of high density, good ductility, large yield strength and high tensile strength. This is because the spherical-crystal tungsten powder obtained by calcination and hydrogen reduction of spherical single-crystal ammonium paratungstate has large loose apparent density and good fluidity. And it is easy to fill the die cavity. Also, it makes the density of compact uniform. The W-Ni-Fe heavy alloy prepared by spherical tungsten powders…